Revealing mistake: In the scene with the games console the controller isn't on and it is either not attached to a PS3 or the PS3 is off. You can tell because if the controller was on there would be a solid red light and even if it was just charging there would be a blinking red light.

Factual error: SPOILER: Amy Dunne returns covered with blood. After being at the hospital, and in the interview/questioning, she is still covered with blood. After being medically examined, she would have been washed clean, not just dressed over all the mess. But it gets worse; when returning to Nick in their house, she has a crisp hospital garment, but is still covered in blood! And it gets even worse; when they are in the shower, the blood on her body, which by now would have been at least a day old, would have been dried, caked and brownish color, but what she washes off is very fresh.

Plot hole: During the hospital interview with the detectives and police, Amy explains that she was kidnapped at the front door by Desi Collings. Neither lead detective Rhonda Boney nor any other cop enquires how massive amounts of her blood ended up on the kitchen floor, or how the living room was trashed.

Trivia: Hollywood actress Reese Witherspoon was a fan of the novel and purchased the rights, intending to play the role of Amy herself. However, once David Fincher was attached as director, she opted to serve only as a producer, realizing she wasn't right for the role.

Trivia: Tyler Perry was reportedly not aware of director David Fincher's body of work, and was cast without knowing Fincher was directing. Perry has stated that he likely wouldn't have taken the role if he knew about the darker work Fincher is generally involved in, but stated that he was glad he did take the role in the end.

Chosen answer:That may have been what she was doing. Amy was attempting to make it look like she'd been repeatedly raped by Collins, so she was doing various things to herself, like using a bottle to self-inflict trauma onto her privates to look like forced sex.